Here's a doc with some key notes:
hope that helped <3
To my mind, the answer ( B ) is the inappropriate sentence. In a formal writing informal tone must be avoided as well as colloquial expressions.
The verb form that is used to indicate present perfect tense is have + verb - ed.
For example:
I <u>have painted </u>a beautiful painting.
C is the complex sentence because it contains the word while and an independent and dependent clause! :)
